To reduce alcohol-related traffic fatalities among youth, on January 1, 1994, California implemented a "zero tolerance law." Any driver under age 21 who is stopped with a measurable blood alcohol, a civil offense, will immediately have his/her drivers license administratively suspended for one year. Of the 17 states to adopt zero tolerance for youth, California is the largest and has over 90% alcohol testing of fatally injured drivers, thereby permitting the most precise evaluation to date of the law's effects on reducing fatal alcohol-involved crashes. A quasi- experimental study will compare California to 6 western states that do not have zero tolerance laws: Washington, Nevada, Idaho, Wyoming, Colorado, and Texas. Earlier studies have shown that active publicity campaigns at the local level can increase the impact of lower legal blood alcohol limits, but the effects of highly publicized intensive enforcement have not been studied. Within California, a second quasi-experimental study will be conducted. Four communities-Oceanside, Salinas, Santa Barbara, and Vallejo-will undertake widely publicized roadblock and roving patrol police enforcement incorporating the use of the passive alcohol sensor. They will be compared to Stockton, Santa Cruz, Orange, and Modesto, California. In both the state and community studies, five years of pre-law crash and injury crash data will be compared to three years of post-law data. Whether the proportion and total numbers of fatally and non-fatally injured drivers age 16-20 who have positive blood alcohol test results declines in California and particularly in enforcement program cities after passage of the law relative to companion areas will be monitored. Publicity campaigns about alcohol-impaired driving and police and court enforcement data will also be monitored at the state and community level. A random digit dial survey of 1,000 California 16-20 year olds and l ,000 in the comparison states will be completed in the first quarter of 1994 immediately after the implementation of the zero tolerance law assessing the attitudes of teenagers regarding drinking and driving, knowledge of current laws, perceived likelihood of alcohol-impaired drivers being stopped by the police, breath tested, and having their license suspended. Frequency of driving after drinking and heavy drinking will be recorded as will alcohol procurement and drinking practices. To monitor change these surveys will be repeated at annual intervals in 1995 and 1996 as will surveys of 750 16-20 year olds in 1994 and 1996 in the rest of the nation. Within California surveys of adolescents in each of the four comparison communities have been in place for 12-18 months. These will be augmented with items specifically relevant to the new law and will be continued- through 1996. The combination of community and state level quasi- experimental evaluation and the high level of blood alcohol testing in California will permit the most comprehensive and rigorous test to date of a zero tolerance law.